farheen farheen - 2 months ago 27
Python Question

How to replace dataframe column values with dictionary keys?

Suppose I have a dictionary:

dict = {"1" : "A", "2" : "B" , "3" : "C"}


and a data frame

df = pd.DataFrame()
df["ID"] = pd.Series(["A","B","C"])
df["Desc"] = pd.Series(["Fruits","Vegs","Meat"])


The dataframe will look like this:

enter image description here

How would I replace values in column
df["ID"]
with dictionary keys so that I have
1,2,3
in
df["ID"]
instead of
A,B,C
?

Answer Source

First create a reverse mapping:

In [363]: dict2 = {v : k for k, v in dict_.items()}

The assumption made here is that your values are unique. Now you can use pd.Series.replace:

In [367]: df.ID = df.ID.replace(dict2); df
Out[367]: 
  ID    Desc
0  1  Fruits
1  2    Vegs
2  3    Meat

Alternative solution with pd.Series.map:

In [380]: df.ID = df.ID.map(dict2); df
Out[380]: 
  ID    Desc
0  1  Fruits
1  2    Vegs
2  3    Meat

Also, I recommend you use a different name than dict, because there's already a builtin with that name.